Method of producing a high vacuum in vessels



Nov. 1, 1927.

D, s. GUSTIN METHOD OF PRODUCING A HIGH VACUUM IN VESSELS I Filed Sept. 6, 1922 'F'IG- 1 T0 vAcul/M PU/ mvamo n DAN/EL anus-n "BY ATTORNEY Patented Nov. 1, 1927.

UNITED STATES 1,647,618 PATENT OFFICE.

DANIEL SNYDER GUSTIN, F NEWARK,- NEW JERSEY, ASSIGNOR T0 WESTINGHOUSE LAMP COMPANY, A CORPORATION PENNSYLVANIA.

METHOD OF PRODUCING A HIGH VACUUM IN VESSELS.

Application filed September 6, 1922.

This invention relates to a method of producing a high vacuum in vessels and more particularly to the evacuation of electric incandescent lamp bulbs, radiotron bulbs and 6 the like.

An object of the invention is to produce a high degree of vacuum in a vessel.

Another object of the invention is to produce a high vacuum by producing a physical 10 change in a gas within a vessel.

A further object of the invention is to create a high vacuum in a vessel in an expeditious, simple and economical manner.

Other objects and advantages will be ap parentfrom the following description.

It is the usual practice to provide a vacuum in a vessel, such as an electric incandescent lamp bulb, by the employment of one or more vacuum pumps. The pumps are designed to produce different degrees of vacuum and successively increase the vacuum until a proper degree is reached. Diiiiculty is, however, encountered in obtaining the high degree of vacuum necessary for certain devices, particularly radiotron bulbs.

After a bulb has been evacuated to the highest possible degree within the capacity of the pumps, a small amount of residual gas remains in the bulb to the detriment of 80 the subsequent life of the device, and the present invention aims toremove the greater part of this residual gas by displacing it with another gas and finally removing the substituted gas, with the result that a high .35 degree of vacuum is obtained.

To accomplish the above, I may first evacuate a vessel to a suitable degree and then displace any gas remaining therein by a selected gas such, for example, as phosphorus 40 vapor. The substitute gas may be caused to completely displace the residual gas by flushing the vessel therewith, which operation may be repeated until only the substitute gas remains. The substitute gas however, be introduced into the vessel by difiusion during the removal of the air from the vessel and, if so, I effect a physical change in the substitute gas to remove it.

The evacuation of vessels for use as electric-incandescent-lamp or radiotron bulbs requires the use of comparatively expensive pumps in order to produce a high vacuum, that is, to reduce the residual gas left in the bulb to an extremely low pressure. It

is practically impossible to remove the last Serial No. 586,461.

traces of such residual gas by mechanical means, even with the most highly eflicient pumps.

My invention provides a method of remov ing or rendering inactive any residual gas that may be left in a vessel after the vessel has been exhausted by mechanical means, such as the usual vacuum pumps. Since the final removal of thegas is notperformed by a pump, it is obvious that less expensive me chanical vacuum-producing apparatus may be employed.

I have found that a high vacuum may be produced by replacing the air normally withn a vessel by a given gas and finally removmg the gas by passing therethrough a hightension discharge of electricity to eliminate the gas. Any gas may be used which will conduct such a discharge and undergo a physical change from vapor to a non-volatile solid, with substantially no vapor-tenslon. Phosphorus vapor has been found to give good results.

A preferred method of practicing my invention is to place a chamber containing phosphorus vapor in communication with an exhaust system adapted to evacuate one or more bulbs or vessels and it has been foundthat, either by diffusion or otherwise, the phosphorus vapor will replace all the gas in the system in a short period of time, thus, when the vessels have been sealed off, the residual gas, as usually found, will have been replaced by the phosphorus vapor. The vessels may then be subjected to a hightension electrical discharge. At first, astrong glow will be observed as the discharge passes through the gas; after two or three flashes, however, no glow will be observed, which indicates that there is no longer a conducting medium within the vessel. The action of the high-tension electricity upon the phosphorus is such hat a physi-- cal change takes place and phosphorus is solidified, in the form of what is believed to be red phosphorus, and is precipitated upon the walls of the vessel, and a high or fine vacuum is thus produced.

The invention will be more clearly un derstood by reference to the accompanying drawings, in which, I

Fig. 1 is a side elevation of a vessel to be exhausted, a vapor chamber and suitable tube connections;

Fig. 2 is a similar view of an evacuated ,The bulb may be heated in the usual manner to drive out moisture.

The tubing system 8 may be of the three-way type, one opening 9 being suitably connected to a pump (not shown), and another opening 10 being connected, by a section of tubing 11, to the mouth of a vessel 12. A valve or stop-cock 13 may be suitably disposed at the mouth of the vessel 12 to regulate the outlet of the contents of the same, and a cock 14 may be provided to open or close the lineleading to the pump. The third opening 15 of the tubing system 8 is connected by the tubing 7 to the exhaust tube 6 of the bulb, the opening 15 being provided with a valve 16.

For the purpose of indicating the vacuum in the bulb, tubing system and connections thereto, a vacuum gauge 17 is provided.

As illustrated in Fig. 2, a bulb 4, after being evacuated by the pump and tipped off, is so placed that the greater part of its surface is in close proximity to an electrode in the form of a brush 18, and the leadingin wires of the bulb are preferably connected to a contact member 19. The electrodes 18 and contact member 19 maybe connected, through conductors 21 and 22, with a high-' tension electrical flow from any suitable generator (not shown It will be understood that the electrical discharge passes between the external electrode 18 and an internal electrode, which, in the case of a lamp, consists of certain conducting portions of the mount; for example, the leading-in wires and the filament. By the use of an electrode of the brush type, the discharge acts to widely distribute the par ticles resulting from the physical change produced in the vapor. If desirable, however, an electrode 23 such as shown in Fig. 3 may be provided. The electrode 23 being of relatively small area, may be placed at the base of the bulb and, when a dlscharge is passed through the vapor 'to solidify it, the particles thereof will be concentrated and con fined within an area of the bulb equal to the surface of the electrode 23, thus, the position of the solidified matter may be controlled and the deposit restricted to any given portion of the bulb.

In practice, the chamber 12, containing white phosphorus vapor, may be connected by the tubing 11 to the system 8, the opening 9 being then connected to an exhausting apparatus and a vessel 4 being connected, by a suitable exhaust tube, to the opening 15.

Assuming that the valves are all closed, the valves 14 and 16 may then be opened and the vessel exhausted to any suitable degree,-

depending upon the degree of the ultimate vacuum required. The valve 14 may then be closed and the valve 13 opened which will result in the passage of phosphorous vapor to the vessel by reason of the difference in pressure between the vessel 4 and the chamber 12, the pressure of the vapor being the greater. The valve 13 may then be closed and the valve 14 opened, causing an evacuation of the vapor from the vessel 4. The operation of filling the vessel with vapor may be repeated until all the air that may have remained in the vessel after the "mechanical exhaust is displaced by phosphorus vapor. The filling and flushing of the vessel 4 may be repeated any number of times. It has been found, however, that one flushing is suflicient for vacuum-type incandescent electric lamps.

It is obvious that, if desirable, the vapor may be generated as needed, in which case, a quantity of phosphorus may be provided in the chamber 12 and heated by any suit-- able means to vapor form.

When the vapor has completely displaced the residual gas in the vessel, the vessel may be tipped or sealed 01f by the usual fires 23, indicated in dotted lines in Fig. 1, and the vessel may then be subjected to a hightension discharge to eflect the physical change in the gas, and a high vacuum will result. In so far as is known, the effect of the electrical. discharge through the vapor is change the white-phosphorous vapor to solidor red phosphorus, the high-tension discharge having caused a change in the character of the gas leaving a substance, which is nonvolatile or with substantiall no vapor tension at room temperatures, an a fine vacuum is produced with but a relatively small amount of work by mechanical means, such as the pumps.

As above described, the phosphorus may be flushed into the vessel 4 but it has also been found that good results are obtained by permitting the vapor to difiuse into the vessel 4. Difi'usion-is accomplished by opening all the valves and operating the pump to evacuate the system. In a relatively short time the gas within the vessel 4 will be replaced by the phosphorus vapor from the chamber 12 by diffusion. The time required depends on the size of the vessel 4 and other factors and ma be readily determined in a given instance y experiment. The vessel may be tipped off and the high-tension discharge passed through the vapor, with the result as above set forth.

The production of a high vacuum by my method has many advantages; for instance, when employing my method in connection with the manufacture of lamps, the flashing operation, as now practiced, may be-omitted.

It is well known that lamps are flashed, to clean-up residual gases, by the activation of a getter, such as magnesium, provided in the form of a small deposit upon a portion of the filament of the lamp, it being then customary to bring the filament to a state of incandescence to activate the getter to improve the vacuum. The lighting of the lamp, however, changes the structure of the filament and renders it relatively brittle and liable to rupture during transportation or handling incident thereto.

It is evident that, when employing my method, the residual gas is disposed of without the necessity of lighting the filament, and a lamp may, therefore, be shipped to the .user with the filament in its ori inal state and thus enable it to better resist pm or impacts during shipment.

While I have shown and described what, at the present time, may be considered a preferred arrangement for practicing my invention, it is to be understood that the same is merely'illustrative, and modifications may be made therein which fall within the spirit and scope of. the appended claims.

What is claimed is:

1. The method of evacuating a vessel which comprises flushing said vessel with a vapor until the vessel contains the said va or only and passing an electrical discharge etween an external electrode and an electrode within said vessel to effect a physical change in said vapor.

2. The method of evacuating a vessel which comprises displacing. air normally within said vessel with a vapor, passing an electrical discharge through said vessel to solidify the vapor and in controlling the position of the resultant solid within the vessel.

In testimony whereof, I have hereunto subscribed my name this fifth day of September- 1922.

DANIEL SNYDER GUSTIN. 

